4th Order Bandpass. 8" woofer

[Bobbytwonames 5,000+ posts]

If it's only one of them it's likely to one closest to the port opening inside the box. Since it has the shortest path it unloads first. Ideally you want the subs to be equal distance from the internal port opening but that can't happen in every case for obvious reasons.

On moderate power systems you can get away with alotmof things but once you start throwing a lot of power these small issues start to show up. In your case you are probably already close to the others bottoming out at the same time. That one is just an early warning lol

It is the closest one to the end of the port inside the box. I turn it down whenever I hear it. I try not to go max demo on anything under 30hz. I can get it to bottom out on cue at 28hz. I can literally predict when it's going to happen. 28-30 volume at a soft clip. Guaranteed.

 

[Bobbytwonames 5,000+ posts]

If it's only one of them it's likely to one closest to the port opening inside the box. Since it has the shortest path it unloads first. Ideally you want the subs to be equal distance from the internal port opening but that can't happen in every case for obvious reasons.

On moderate power systems you can get away with alotmof things but once you start throwing a lot of power these small issues start to show up. In your case you are probably already close to the others bottoming out at the same time. That one is just an early warning lol

This one or that one. The port is 22-¼" long. The box is about 53-½" long.

 

[winkychevelle 10+ year member]

This one or that one. The port is 22-¼" long. The box is about 53-½" long.

View attachment 43114

Yea it's the sub unloading as resistance from the port decreases and the box Storts to act like free air.

Probably not any major issue. I had the same issue with my Dayton ho 10s. I thought they were just bottoming out but once I swapped in my sa10v2 and the sundown's we're doing the same a quick box mod to go from 1 port on 1 side to 2, one on each side completely eliminated my issue.

Kinda want to try the Dayton's again after that learning experience

 

[Jake321]

I would do a 4inch aero personally vent air speeds far exceed the 40m/s max with the 3inch port. They even exceed it with the 4inch port once your exceed 1000w.

At 1000w and a 4inch port flared on both sides you are sitting just below 40m/s so you shouldn't get port noise it's only 16-17inches or port length for 38hz

This is my DD712. It's right at the maximum cubes 2.73.
The Port is 33HZ.
The Subwoofer is inverted (but not reversed).
Was wondering if it's bad to push into the enclosure.
Was also wondering if I should go bigger with the Port?

Thanks I'll go with the 4" for the: DD608!

 

[winkychevelle 10+ year member]

This is my DD712. It's right at the maximum cubes 2.73.
The Port is 33HZ.
The Subwoofer is inverted (but not reversed).
Was wondering if it's bad to push into the enclosure.
Was also wondering if I should go bigger with the Port?

Thanks I'll go with the 4" for the: DD608!

That box needs a 6inch aero or 2 4s and inverting doesn't hurt the box any it just subjects you to more motor noise if there is any.

 

[Bobbytwonames 5,000+ posts]

This is my DD712. It's right at the maximum cubes 2.73.
The Port is 33HZ.
The Subwoofer is inverted (but not reversed).
Was wondering if it's bad to push into the enclosure.
Was also wondering if I should go bigger with the Port?

Thanks I'll go with the 4" for the: DD608!

Port is too small man. Put a 6" in that same box.

 

[Jake321]

Port is too small man. Put a 6" in that same box.

2.73" cubes 6" Port= 21" long 6"Port!

 

[Jake321]

Port is too small man. Put a 6" in that same box.

Do PVC Pipes need flares?

 

[winkychevelle 10+ year member]

Do PVC Pipes need flares?

You could likely get away without the flares with a 6inch port. Bigassports usually has 6inch ports in stock.

 

[Jake321]

You could likely get away without the flares with a 6inch port. Bigassports usually has 6inch ports in stock.

6" Port is 21" long 33HZ. 2.73 Cubic Feet.

How do you guys work with giant length ports?

 

[winkychevelle 10+ year member]

6" Port is 21" long 33HZ. 2.73 Cubic Feet.

How do you guys work with giant length ports?

Using pipe you can use fittings to turn the port.

And I'm pretty sure 2 4inch ports would be slightly shorter because it's a few sq inch's smaller.

As far as how we fit ports we design the poxes with the ports in mind

 

[Bobbytwonames 5,000+ posts]

2.73" cubes 6" Port= 21" long 6"Port!

Hang it out of the box if you have to.

 

[audiobaun 5,000+ posts]

Do PVC Pipes need flares?

NO

 

[deez283 10+ year member]

You might, and you might hear it or you might not. 12in² per cube in a slot port is on the small side and is best kept for low xmax subs. The higher the xmax the more port area you need. It varies subs to sub and by different power levels.

all of this can me calculated. Generally 40m/s is what you want to stay under. My last 3.31 at 36hz with 2 4inch aeros was at like 45m/s and I didn't hear the ports.

In a trunk port noise might not be heard. Behind the seat of your truck it might be muffled enough that you don't care. Or you vehicle might just me loud enough with road noise you don't hear it. Alot of really big builds you would hear the car flexing louder than the port noise.

And like you said we don't all roll around with our systems maxed out

Interesting read
how much is too much port area? | Car Audio Forum | CarAudio.com

 

[winkychevelle 10+ year member]

Interesting read
how much is too much port area? | Car Audio Forum | CarAudio.com

It varies based on the sub. Really it depends on xmax and piston area.

Low xmax subs don't need as much port area, same for smaller diameter subs.

It pretty much is the result of the total volume the sub can displace being shoved through the port. The smaller the port the higher the port air velocity. At certain points it turns into noise.

Too much port area results in a narrow bandwidth before the port unloads. That narrow bandwidth can result in excellent efficiency inside that bandwidth. Think burp box.

15in² is what I try and use for regular 15-25mm x-max subs. Aeros I run 7-10 usually to save space